1. Field of the Invention
This invention relates generally to systems for monitoring welding operations, and more particularly to a non-contact optical sensor for separating and quantizing the radiation spectrum emitted from the weld puddle of a weld bead to analyze same.
2. Discussion of Related Art
The cost of locating and repairing defects in welded products can be a major portion of construction costs. Weld inspection alone can constitute 25%-40% of total weld fabrication costs. Thus, it would be desirable to have a real-time weld quality monitor which can provide an alarm signal or interrupt the welding process when defects in the weld bead are occuring, thus precluding costly rework.
Direct quantitative measurements of certain parameters of welds during the welding process have not been possible for several reasons. In particular: (a) high weld temperatures consume and destroy sensors proximate to the weld area; (b) contacting sensors introduce a discontinuity of the weld process causing data uncertainty; and (c) in the case of manual welding, the subjectiveness peculiar to the welder is indeterminate and variable.
Presently, some indirect measurements of weld beads are made through the use of thermocouples and the like, but these techniques exhibit time lags, averaging effects and other factors that mitigate the validity and reproducibility of the information obtained.
Attempts at providing systems for measuring various welding parameters have been made in the past. For instance, U.S. Pat. No. 3,236,997 to Johnson et al shows a system for controlling the length of a welding arc in a consumable electrode welding apparatus. A photosensitive transducer, such as a photodiode, is positioned to sense the illumination emitted by the arc between the consumable electrode and the workpiece. The sensing system includes a tubular pipe and a mirrored surface to project a long beam of detectable illumination from the arc through the pipe to the photodiode sensor.
U.S. Pat. No. 3,262,006 to Sciaky et al shows a welding control system having a light sensitive probe incorporating an arrangement using fiber optics to conduct the illumination from an area adjacent the weld to a sensor or phototransducer which is disposed at a remote location. An ultraviolet filter can be used in the system to in effect see through the flame portion of the arc to the inner plasma portion. This approach operates to maintain the electrode at a substantially constant distance from the the workpeice.
U.S. Pat. No. 3,370,151 to Normando shows a weld control system using radiant energy detector scanning. A photocell is employed which is sensitive to infra-red radiation.
Finally, U.S. Pat. No. 3,602,687 to Pollock shows an arc length control comprising two pick-up sensors which are spaced at preselected intervals along the arc path.